It is the intent of the investigators to develop a new diagnostic test for use during pregnancy to identify women at elevated risk for preterm delivery (PTD). An immunoassay using a monoclonal antibody directed against oncofetal fibronectin (fFN), a pregnancy-related protein of placental origin found in the amniotic fluid, has been standardized for this purpose. Preliminary studies have shown that greater than 50 ng/ml of fFN was present in the cervicovaginal secretions of 81 percent of women at 23 to 36 weeks of gestation who sought medical attention for suspected rupture of membranes of PTD, in contrast to only 20 percent (p less than 0.001) of 267 women with uncomplicated term pregnancies. This difference could not be explained by differences in gestational age at sampling, cervical dilation or presence of blood in the secretions. The primary objective of Phase I will be to characterize the relationship between cervicovaginal fFN expression and incidence of PTD in a longitudinal study of 100 high risk pregnancies.In Phase I, the investigators will design a prospective clinical trial to thoroughly evaluate the diagnostic efficacy of an anti- fFN assay for commercial application.